Creating Parallel Tasks from a SharePoint 2010 Workflow

A task is a key component of any Microsoft SharePoint 2010 workflow. Your workflow might need to assign and track parallel tasks. You can create parallel SharePoint tasks from a Microsoft Visual Studio 2010 workflow project.

To create parallel tasks in a workflow, you must use a ParallelActivity activity in the workflow.
Creating the Workflow
When you create parallel tasks in a SharePoint workflow, begin by creating the tasks outside the ParallelActivity activity. Then, use a ParallelActivity activity to track when each parallel task is changed or completed. Figure 1 shows the complete workflow with two parallel tasks.
Figure 1. Workflow with parallel tasks

C#

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namespace ParallelTasks
{
    public sealed partial class Workflow1 : SequentialWorkflowActivity
    {
        public Workflow1()
        {
            InitializeComponent();
        }

        public Guid workflowId = default(System.Guid);
        public SPWorkflowActivationProperties workflowProperties = 
          new SPWorkflowActivationProperties();
        public Guid task1Id = default(System.Guid);
        public SPWorkflowTaskProperties task1Properties = 
          new Microsoft.SharePoint.Workflow.SPWorkflowTaskProperties();
        public Guid task2Id = default(System.Guid);
        public SPWorkflowTaskProperties task2Properties = 
          new Microsoft.SharePoint.Workflow.SPWorkflowTaskProperties();
        public bool task1Complete = false;
        public bool task2Complete = false;
        public SPWorkflowTaskProperties task1AfterProperties = 
          new Microsoft.SharePoint.Workflow.SPWorkflowTaskProperties();
        public SPWorkflowTaskProperties task1BeforeProperties = 
          new Microsoft.SharePoint.Workflow.SPWorkflowTaskProperties();
        public SPWorkflowTaskProperties task2AfterProperties = 
          new Microsoft.SharePoint.Workflow.SPWorkflowTaskProperties();
        public SPWorkflowTaskProperties task2BeforeProperties = 
          new Microsoft.SharePoint.Workflow.SPWorkflowTaskProperties();
        public Guid TaskStatusFieldId = 
          new Guid("c15b34c3-ce7d-490a-b133-3f4de8801b76");
        public String task1Outcome = default(System.String);
        public String task2Outcome = default(System.String);

        private void onWorkflowActivated1_Invoked(object sender, 
          ExternalDataEventArgs e)
        {
            // Save the workflow ID.
            workflowId = workflowProperties.WorkflowId;
        }

        private void createTask1_MethodInvoking(object sender, 
          EventArgs e)
        {
            // Create the first task.
            SPUser approver1 = 
              GetUserFromPickerString(workflowProperties.Item
                ["Team Leader"].ToString());
            SPUser employee = 
              GetUserFromPickerString(workflowProperties.Item
              ["Employee"].ToString());
            task1Id = Guid.NewGuid();
            task1Properties.AssignedTo = approver1.LoginName;
            task1Properties.Description = 
              "Approve Vacation Request for " + employee.Name;
            task1Properties.Title = "Vacation Request Approval";
        }

        private void createTask2_MethodInvoking(object sender, 
          EventArgs e)
        {
            // Create the second task.
            SPUser approver2 = 
              GetUserFromPickerString(workflowProperties.Item
              ["Department Head"].ToString());
            SPUser employee = 
              GetUserFromPickerString(workflowProperties.Item
              ["Employee"].ToString());
            task2Id = Guid.NewGuid();
            task2Properties.AssignedTo = approver2.LoginName;
            task2Properties.Description = 
              "Approve Vacation Request for " + employee.Name;
            task2Properties.Title = "Vacation Request Approval";
        }

        private void task1NotComplete(object sender, 
          ConditionalEventArgs e)
        {
            e.Result = !task1Complete;
        }

        private void task2NotComplete(object sender, 
          ConditionalEventArgs e)
        {
            e.Result = !task2Complete;
        }

        private void onTaskChanged1_Invoked(object sender, 
          ExternalDataEventArgs e)
        {

            // Check whether task 1 is completed.
            string taskStatus = 
              task1AfterProperties.ExtendedProperties
              [TaskStatusFieldId].ToString();
            if (taskStatus.Equals("Completed"))
                task1Complete = true;
            else
                task1Complete = false;
        }

        private void onTaskChanged2_Invoked(object sender, 
          ExternalDataEventArgs e)
        {

            // Check whether task 2 is completed.
            string taskStatus = 
              task2AfterProperties.ExtendedProperties
              [TaskStatusFieldId].ToString();
            if (taskStatus.Equals("Completed"))
                task2Complete = true;
            else
                task2Complete = false;
        }

        private void completeTask1_MethodInvoking(object sender, 
          EventArgs e)
        {
            // Finalize task 1.
            task1AfterProperties.PercentComplete = 100;
            task1Outcome = "Reviewed";
        }

        private void completeTask2_MethodInvoking(object sender, 
          EventArgs e)
        {
            // Finalize task 2.
            task2AfterProperties.PercentComplete = 100;
            task2Outcome = "Reviewed";
        }

        private SPUser GetUserFromPickerString(string PickerString)
        {
            string id = string.Empty;
            try
            {
                id = PickerString.Substring(0, 
                  PickerString.IndexOf(';'));
                return workflowProperties.Web.SiteUsers.GetByID
                  (int.Parse(id));
            }
            catch { return null; }
        }
    }
}

When you create parallel tasks in a SharePoint workflow, you must first use the CreateTask activity to create tasks. Then you can use the ParallelActivity activity to track when the tasks are changed or completed.
Following is a review of the activities:

• The CreateTask activity creates a new task in a SharePoint list.
• The OnTaskChanged activity checks whether the task is complete each time a user changes the task in some way.
• The CompleteTask activity finishes the task and allows the workflow to continue.
• The ParallelActivity activity causes the tasks to run in parallel so that they can be completed in any order.